The invention relates to a method for monitoring the proper functioning of an integrated circuit. The supply voltage of the integrated circuit is monitored and dips in the supply voltage that are ascertained in the process are signaled.
The proper functioning of devices of every type is, understandably, the intended objective of every development. This applies in particular to integrated circuits because in their case extremely small errors can have disastrous effects. Efforts are continually being made, therefore, to increase the reliability of integrated circuits, but this is not exactly easy because of the increasing size of integrated circuits and their packing density.
Despite all previous efforts, it has not been possible heretofore to fabricate and to operate integrated circuits completely without errors.
U.S. Pat. No. 5,371,709 describes a method in which a reaction to a supply voltage dip takes place immediately, that is to say without delay That also means, however, that even momentary dips in the supply voltage, which frequently do not even result in a malfunction of the integrated circuit, cause an interruption as a reaction to the voltage dip.
Further methods for monitoring the proper functioning of integrated circuits are described in U.S. Pat. No. 5,199,032, U.S. Pat. No. 5,397,946 and the Published European Patent EP 0 598 475 A2.
It is accordingly an object of the invention to provide a method for monitoring the proper functioning of an integrated circuit which overcomes the above-mentioned disadvantages of the heretofore-known methods of this general type and which further improves the reliability of integrated circuits.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for monitoring a proper functioning of an integrated circuit. The method includes the steps of:
monitoring a supply voltage of an integrated circuit;
ascertaining a dip in the supply voltage; and
effecting a signaling of the dip in the supply voltage only if the supply voltage falls below a given voltage for a given minimum duration.
In other words, the method according to the invention provides that a signaling is only effected if the supply voltage falls below a predetermined voltage for a predetermined minimum duration.
In accordance with another mode of the invention, the signaling of the dip in the supply voltage is effected by outputting a signaling signal having a voltage of substantially zero volts.
In accordance with yet another mode of the invention, the signaling signal is provided as a signal having a value substantially equal to a value of the supply voltage if and as long as no dip in the supply voltage having a sufficient depth and length is present.
In accordance with a further mode of the invention, the monitoring step is carried out only if and as long as an activation signal is applied to a monitoring circuit.
In accordance with yet a further mode of the invention, if the activation signal is not applied, then a signaling signal is output, which corresponds to a signaling signal that would be output if the supply voltage were properly high during an activated monitoring.
In accordance with another mode of the invention, a level of the supply voltage is checked with a reference voltage which is independent of the level of the supply voltage.
In accordance with another mode of the invention, a level the supply voltage is checked dependent on a reference voltage which is independent of the level of the supply voltage.
In accordance with a further mode of the invention, operations, which are influenced by the dip in the supply voltage or which may have been influenced by the dip in the supply voltage, are repeated after an end of the dip in the supply voltage.
The signaling of supply voltage dips makes it possible for the integrated circuit, if required, to induce or cause automatically, through the use of a monitoring circuit or by itself or manually by an operator, a selective repetition of operations which have been carried out during and/or before and/or after a supply voltage dip and, consequently, may have proceeded with errors. Disturbances caused by supply voltage dips can thus be eliminated, as far as their effects are concerned, immediately and in a manner that is entirely unnoticeable to the outside in some instances.
Consequently, a method for monitoring the proper functioning of an integrated circuit has been found which enables the integrated circuit to be operated with a considerably higher reliability than before. The cause of the disturbance that has been identified may lie either within or outside the integrated circuit to be monitored.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for monitoring the proper functioning of an integrated circuit, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.